As a well known pressure type stencil printing device, there is known the one which comprises a pressure plate having an edge hinged to a base, a printing paper supporting table made of elastic material such as a foamed elastomer and placed on the base, and a stencil master plate mounting portion provided on the surface of the pressure plate opposing the printing paper supporting table. Such a stencil printing device is disclosed, for instance in Japanese utility model laid open publication No. 62-196567.
According to such a pressure type stencil printing device, a stencil printing is made by pivotally pressing down the pressure plate by a hand so that the stencil master plate mounted on the pressure plate may be pressed onto the printing paper placed on the printing paper supporting table.
According to a known suction type textile printing device for placing a screen serving as a stencil on textile and dying the textile by depositing dye thereon in a prescribed pattern, the textile is placed on a porous support or a mesh plate having a number of holes provided therein, and with a stencil screen placed over the textile, suction is applied to the porous support or the mesh plate so that the suction is applied, via the textile on the porous support or the mesh plate, to the surface of the stencil screen facing the textile, and the dye deposited on the stencil screen is drawn into the textile through the openings of the stencil screen. Such suction type textile printing devices are disclosed, for instance, in Japanese patent publications (kokoku) Nos. 37-3944, 38-5199 and 44-13797 (U.S. Pat. No. 3,221,648).
To achieve a stencil printing at a prescribed density with a pressure type stencil printing device, a prescribed printing pressure is required, and the required pressure becomes greater as the printing surface area becomes larger.
On the other hand, according to such a stencil printing device, the printing pressure effective in pressing the stencil master plate onto the printing paper placed on the printing paper supporting table is produced by pressing down the pressure plate with a hand for pivoting the same, and is therefore quite limited in magnitude.
Also, to achieve a stencil printing of a uniform density, it is necessary to apply an even printing pressure over the entire printing surface. However, according to such a conventional stencil printing device, because the pressure plate is pivotally supported, and the rotational downward movement of the pressure plate is directly applied to the printing surface as a printing pressure, the printing pressure applied to the printing surface tends to be uneven, and there is some difficulty in obtaining stencil print images of a high level of uniformity. This tendency is particularly pronounced when the printing surface area becomes greater, and with the increase in the printing surface area, obtaining uniform stencil printed images and achieving a practical stencil printing become increasingly more difficult.
In view of such problems, the size of the printing paper for such a stencil printing device is limited to B5 (182.times.257 mm) and A4 (210.times.297 mm).
Furthermore, according to such a stencil printing device, because the pressure acts upon the printing ink deposited on the stencil master plate in the direction to pass across the stencil master plate, even though the printing ink deposited on limited regions of the stencil master plate, the printing ink deposited on the stencil master plate is laterally extended every time a printing pressure is applied to the printing ink, and the amount of wasted printing ink increases. This occurs also when multi color printing is carried by using a stencil master plate on which printing inks of various colors having the consistency or thickness sufficient to retain their shapes are individually deposited on the stencil master plate. In this case, not only a substantial amount of printing ink is wasted but also the printing inks of various colors laterally extend to such an extent as the number of printed copies increases that the printing inks of different colors may get mixed with each other, and a proper color printing with distinct colors may be made impossible.
The previously mentioned suction type textile printing device is applicable only to textile and other air-pervious materials because the suction is applied to the surface of the stencil screen facing the printing surface through a layer of material primarily consisting of the textile, and therefore cannot be applied to a stencil printing device for printing normal paper. Because, according to the suction type textile printing device, the suction transmitted to the suction holes of the porous support or the mesh of the mesh plate is applied to the surface of the stencil screen facing the printing surface via the material to be printed, and the dynamic action of the suction causes the dye deposited on the stencil screen to be drawn into the material to be printed, the suction is distributed over the stencil screen according to the pattern of the suction holes in the porous support or the mesh pattern of the mesh plate, and therefore tends to be uneven. Hence, even when the printing paper is air impervious to a certain extent, it still is not possible to obtain printed images of uniform density as opposed to the case of printing on textile.